Ch. 3 - Experimental
3. EXPERIMENTAL
This Chapter briefly describes the methods, materials and other experimental techniques used
to generate data for the thesis work. The principles involved in electroanalytical techniques
such as cyclic voltammetry, chronoamperometry and chronopotentiometry have been
discussed. The spectroscopic techniques UV-Visible spectrophotometry and inductively
coupled plasma – optical emission spectroscopy (ICP-OES) used for quantitative
determination of ruthenium are described. Other experimental techniques such as X-ray
photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared
spectroscopy (FTIR) and Transmission electron microscopy (TEM) are briefly discussed.
3.1 MATERIALS AND CHEMICALS
3.1.1 Chemicals
All the chemicals used for experimental work were of analytical grade and procured from the
following companies:
M/s. Arora Matthey, Kolkata: Ruthenium(III) chloride (RuCl3.3H2O) powder, Ruthenium
nitrosyl nitrate (1.7% W/V) in 9 M nitric acid and Silver nitrate.
M/s. Loba Chemie, Mumbai: Ammonium ceric nitrate ((NH4)2Ce(NO3)6, Assay: 98 %);
Hydrogen peroxide(H2O2), Assay 30%
M/s. SD fine chem. Ltd, Mumbai: Cerium (III) nitrate hexahydrate, Assay: 90%
Merk, Germany: 1 10-phenanthroline, Assay: 99.5%, Water content: 8.5-10%;
Hydroxylammoniumchloride, Assay: 99%, Water content: 5%
Jiangsu Huaxi International Trade Co. Ltd. China: Ethanol, Assay: 99.9%
Hi-Pure fine chem. Industries, Chennai: Sodium Hydroxide, Assay: 99%
51
Ch. 3 - Experimental
All other nitrate salts and oxides used for the preparation of simulated high level liquid waste
(SHLLW) were procured from M/s. Alfa Aesar, UK, Merck, Germany, Sigma Aldrich, USA,
and Strem Chemicals, USA. Nitric acid (AR Grade; Assay: 69 %) used throughout this study
was supplied by M/s. Fischer Chemicals Ltd, Chennai.
3.1.2 Materials
Platinum, Glassy carbon and Gold working electrodes and Ag/AgCl reference electrode were
procured from M/s. Metrohm India Pvt Ltd, Chennai. Platinum mesh electrodes of different
surface area used for electro-oxidation experiments were supplied by M/s. Ravindra Heraeus
Ltd, Udaipur. One end closed, reaction bonded silicon nitride (RBSN) diaphragm tube used
in electro-oxidation study was fabricated by CGCRI, Kolkata.
3.2 INSTRUMENTATION AND FACILITIES
3.2.1 Electrochemical System
The electrochemical studies cyclic voltammetry, chronocoulometry and chrono amperometry
were carried out using Autolab (PGSTAT- 030; procured from M/s. Eco-Chemie, the
Netherlands) equipped with an IF 030 interface. General Purpose Electrochemical (GPES)
System Version 4.9 installed in a personal computer was used for data acquisition and
analysis. Electro-oxidation studies with two electrode system were performed by applying
either constant current or constant potential using regulated DC power supply DSC20-50E
(supplied by M/s. AMKET, USA).
3.2.2 UV-Visible Spectrophotometer
Quantitative analysis of pure ruthenium containing solutions in nitric acid media was carried
out from the absorption spectra recorded using Chemito Instruments Pvt Ltd - UV 2600
double beam Spectrophotometer with the wave length range 190 -1100 nm. Quartz cuvettes
of path length 1 cm were used for all analysis. Ruthenium concentration in pure Ru(NO3)3
52
Ch. 3 - Experimental
and [RuNO]3+ solution was estimated spectrophotometrically using 1-10, Phenanthroline as
chromogenic reagent [1]. However this method of analysis of ruthenium was not applicable
in case of SHLLW solution due to interference of other metal. Speciation of various
[RuNO]3+ complexes was carried out using this technique.
3.2.3 XRD
X-ray diffraction (XRD) analysis was carried out using INEX-XRG-3000 diffractometer with
a curved position sensitive detector using Cu Kα1 (0.15406 nm) radiation with grazing angle
(ω) as 5°.
3.2.4 XPS
X-ray photo electron spectroscopic (XPS) measurements were carried out using SPECS make
(Germany) spectrometer. Al Kα was used as the X-ray source at 1486.71 eV. The anode was
operated at a voltage of 13 kV and source power level was set to 300 W. An Ar+ ion source
is also provided for sputter-etch cleaning of specimens. It was operated at 5 kV and 10 µA.
The system sputters approximately at the rate of 10Ao/min for standard silver sample. Spectra
were collected using the PHOIBOS 150 MCD-9 analyzer with a resolution of 0.6 eV at the
pass energy of 10 eV. The spectrometer was calibrated using a standard silver sample for the
Ag 3d 5/2 peak at 368.3 eV. Data were processed by Specslab2 software. The binding energy
of C 1s transition from adventitious C at 285 eV was used as the reference to account for any
charging of the sample and the peak positions were compared with standard values for
identification of different elements and their oxidation states.
3.2.5 TEM
Microstructural analysis was carried out with LIBRA 200FE, a high resolution transmission
electron microscope (HRTEM) operated at 200 kV with a field emission electron source and
equipped with high angle annular dark field detector and in-column Omega filter for
53
Ch. 3 - Experimental
spectroscopic analysis. Specimen for TEM analysis was prepared by the standard method for
powder TEM specimen preparation; ultrasonication of the sample powder in ethanol,
followed by a drop placed on carbon coated Cu TEM grid and dried for evaporating the
solvent. Electron energy loss spectra (EELS) were acquired using the in-column Omega filter
in the TEM (Libra 200FE) and the energy resolution of EELS was 0.7 eV.
3.2.6 FTIR
In the thesis work, Fourier Transform – Infra red spectra were recorded from 4000 cm-1 to
500 cm-1 using the FTIR spectrometer (ABB make model) MB3000 with a DTGS (deuterated
triglycine sulphate) detector. Liquid samples were analysed using horizontal ATR
(Attenuated Total Reflectance) accessory. Horizon MB Software was employed to analyze
the spectra. All measurements were made using 32 scans and 4 cm-1 resolution, proper
baseline was selected for each peak.
3.2.7 ICP-OES
The amount of ruthenium in acidic aqueous phase was determined by Optical emission
spectroscopic analysis using the ICP-OES (Jobin Yvon, France) and the standards were
produced by MBH analytical limited.
Atomic spectrometry is the commonly used technique for the determination of trace
concentrations of elements in the sample. Elements in solution can be detected and quantified
by means of optical emission spectrometry with inductively coupled plasma (ICP-OES).
Because of its high sensitivity, ability to perform rapid and simultaneous multi-element
analysis, low detection limit and free from chemical interference, optical emission
spectroscopy is the principal tool of analysis at trace levels [2]. The solution under analysis is
nebulised and the aerosol thus formed is transported to a high-frequency plasma (8,000–
10,000ºC) in which the constituents of the sample solution are atomized, ionized and excited
54
Ch. 3 - Experimental
to higher energy states to produce characteristic optical emissions. The characteristic
emission lines of the atoms and ions are dispersed by a monochromator or polychromator and
the intensity of the lines is recorded in a photo multiplier tube (PMT) detector. The block
diagram of a typical ICP-OES instrument is shown in Fig. 3.1[3]. The intensity of the spectral
lines is proportional to the concentrations of analytes in the aqueous sample; i.e.
quantification by means of external calibration with a linear regression line is possible. The
highest concentration of the standard for a calibration should be greater than the lowest
concentration by a factor of 10-20. The linearity within the working range should be verified.
The coefficient of correlation ‘r’ should be > 0.995.
The wavelengths are selected in
accordance with the required limit of detection and the possibility of interference by other
elements present in the sample solution. In determining the concentration of Ru, the
wavelength of spectral line selected was 245.66 nm and the lowest point of calibration graph
was 0.4 ppm since at this concentration the confidence level was more. Standard solutions
prepared for generating calibration graph were single element standard for pure ruthenium
solution and multi-element standard for SHLLW solution. 1000 ppm of MBH standard
solution of Ru was diluted with required volume to prepare each 10 ml of 0.4, 1, 2, 4, 10 and
20 ppm of standard solutions for calibration. Experiments were initiated by generating
calibration graphs by plotting intensity against known concentration Ru standard and stored
in the computer. A typical calibration graph for Ru in nitric acid medium, showing a linear
relationship between the intensity (as detector count) and concentration is given in Fig. 3.2.
Using this calibration graph the unknown concentrations of Ru in test samples were
determined. The software used for analysis was Jobin Yvon HORIBA – ICP ANALYST
version 5.2. All experiments were carried out as per the operating conditions listed in Table
3.1.
55
Ch. 3 - Experimental
Fig. 3.1 Block diagram of a typical ICP – OES instrument [2]
42000
Ruthenium Calibration
36000
30000
Intensity
24000
18000
12000
6000
0
0
5
10
[Ru] / ppm
Fig. 3.2 Calibration graph for Ruthenium
56
15
20
Ch. 3 - Experimental
Table 3. 1 Operating conditions and description of ICP-OES instrument
RF generator
RF incident power
Inner dia of torch alumina injector
Nebulizer argon gas flow rate
Argon gas flow rate
Signal measurement mode
Spray chamber
Nebulizer type
Pump
Sample uptake flow rate
Polychromator
Resolution
Detector
40.68 MHz
1000 W
2 mm
1 litre/min
12 litre/min (plasma)
Peak jump
Cyclonic
Pneumatic
Peristaltic, three channel
1 ml/min
Paschen-Runge system
0.003 nm
Photomultiplier tube
3.3 PREPARATION OF SOLUTIONS
3.3.1 Ruthenium Nitrosyl Solution
Stock solutions of different concentrations of ruthenium nitrosyl nitrate in nitric acid were
prepared by dissolving the required quantity of ruthenium nitrosyl nitrate stock in appropriate
nitric acid concentrations.
3.3.2 Simulated HLLW Solution
A 27 component, synthetic high level liquid waste solution simulated with fission and
corrosion product elements in 4 M nitric acid was prepared by mimicking the reprocessed
waste of FBTR fuel with a burn-up of 150 GWd/ton and after a cooling period of 1 year. The
chemical form of the elements and their concentration in the simulated waste solution are
listed in Table 3.2. The prepared waste solution was diluted to 6.62 times to bring down the
concentration of ruthenium to 160 ppm (the concentration of Ru envisaged in the first cycle
raffinate) and used throughout the experiments at various concentrations of HNO3 ranging
from 4 to 1 M.
57
Ch. 3 - Experimental
Table. 3.2 The chemical composition of fission and corrosion product elements in simulated
waste solution in 4M HNO3
Element
a
Aga
Concentration of element
(g/L)
0.097
Chemical form used
Ba
0.485
Ba(NO3)2
0.922
Cd
0.046
Cd(NO3)2
0.097
Ce
0.769
Ce(NO3)3·6H2O
2.383
Cs
1.405
CsNO3
2.061
Dy
0.0009
Dy(NO3)3.5H2O
0.0024
Eu
0.051
Eu(NO3)3·6H2O
0.151
Gd
0.032
Gd(NO3)3·6H2O
0.091
In
0.0042
In(NO3)3·6H2O
0.012
La
0.418
La(NO3)3·6H2O
1.300
Mo
1.115
(NH4)6Mo7O27·6H2O
2.052
Nb
0.0006
Nb2O5
0.001
Nd
1.186
Nd2O3
1.383
Pd
1.070
Pd(NO3)2
2.317
Pr
0.410
Pr2O3
0.479
Rb
0.070
RbNO3
0.121
Ru
1.086
RuNO(NO3)3.(H2O)2
Sb
0.017
Sb2O3
0.0204
Sm
0.342
Sm(NO3)3·6H2O
1.010
Sr
0.146
Sr(NO3)2
0.352
Te
0.160
TeH6O3
0.287
Y
0.084
Y(NO3)3.6H2O
0.364
Zr
0.900
ZrO(NO3)3·9H2O
2.28
Fe
0.084
Fe powder
0.084
Ca
0.637
Ca(NO3)2 .4 H2O
3.69
Ni
0.026
Ni(NO3)2·6H2O
0.129
Al
0.062
Al(NO3)3·9H2O
0.862
AgNO3
Quantity
(g/L)
0.153
63.88 ml (1.7 % Ru)
Though Ag is not a fission product, it is included in the simulated waste as it serves as a
mediated redox catalyst in the electro-oxidative dissolution of Pu-rich oxide fuels
58
Ch. 3 - Experimental
3.3.3 Ammonium Ceric Nitrate Solution
Ammonium ceric nitrate solution (1M) was prepared by dissolving the salt in appropriate
concentrations of nitric acid and diluting to required concentrations after standardizing the
prepared solution by conducting potentiometric titration against standard ferrous sulphate.
3.3.4 Nitric Acid Solutions
Nitric acid of different concentrations were prepared by diluting the concentrated acid with
millipore water and the concentrations were estimated by titrimetry against sodium hydroxide
base in the presence of phenolphthalein indicator.
3.4 THEORY OF ELECTROANALYTICAL TECHNIQUES
Electroanalytical techniques are unique tools to investigate several chemical, physical and
biological systems by measuring the potential and/or current in an electrochemical cell and
detailed discussions on the fundamental aspects and applications of these techniques are
covered in standard textbooks [4-9]. A brief summary of the electroanalytical techniques with
relevance to the present study is discussed below.
The species that responds to the applied potential or current is known as electroactive
species. Electrochemical response of an electroactive species is dependent on the mode of
mass transport. The three types of mass transport are (1) diffusion, (2) migration and (3)
convection. Conducting the experiments under quiescent conditions eliminate the convection
mode of transport. Adding large excess of an inert supporting electrolyte eliminates the
migration mode of transport. Thus, the essential mode of mass transfer is made to occur only
by diffusion of electroactive species. The kinetic rate of an electrochemical reaction is
controlled by three processes, namely (a) Diffusion rates of the oxidized and reduced species,
(b) The rate of heterogeneous charge transfer across the electrode/electrolyte interface and (c)
The rates of chemical reactions coupled with charge transfer [9]. These processes dictate the
59
Ch. 3 - Experimental
shape of the electrochemical response for a particular electrochemical system or cell under
investigation.
The electroanalytical techniques are classified into three categories: potentiometry
(where the difference in electrode potentials is measured), coulometry (cell’s current is
measured over time) and voltammetry (the cell’s current is measured while actively altering
the potential). Voltammetric techniques are among the most commonly used electrochemical
transient techniques to study the behaviour of the analyte at an electrode-electrolyte interface.
The voltammetric techniques are broadly classified as potentiostatic and galvanostatic
techniques. In potentiostatic technique the potential of the system is controlled and the
response in the form of current is measured and in galvanostatic technique the current of the
system is controlled and the potential response is measured. The potential of the system
(working electrode against a standard reference electrode) can be varied linearly with time
(scan or sweep methods) or it can be varied step wise incremental with time (step method).
Voltammetric methods such as cyclic voltammetry and linear sweep voltammetry are sweep
techniques (Section 3.4.1) and chronomethods (Section 3.4.2) are step techniques.
3.4.1 Cyclic Voltammetry
Cyclic voltammetry (CV), although one of the more complex electrochemical techniques, is
very frequently used because it offers a wealth of experimental information and insight into
both the kinetic and thermodynamic details of many chemical systems [4] It is the most
versatile electroanalytical technique for the study of electroactive species [10].
CV is one of the most widely used forms and it is useful to obtain information about
the redox potential and electrochemical reaction (e.g. the chemical rate constant) of analyte
solutions. The voltage is swept between two values at a fixed rate and when the voltage
reaches V2 the scan is reversed and the voltage is swept back to V1, as illustrated in Fig. 3.3.
60
Ch. 3 - Experimental
Fig. 3.3 (a): Cyclic voltammetry waveform and (b): Typical cyclic voltammogram; Ep,c and
Ep,a are cathodic and anodic peak potentials respectively.
Voltammogram is the plot of measured current against voltage. The parameters in a
cyclic voltammogram include cathodic (Ep,c ) and anodic (Ep,a) peak potentials, cathodic (ip,c)
and anodic (ip,a) peak currents and half-peak potential, Ep/2. The convention followed in this
thesis is, cathodic current is negative and anodic current is positive and plotted to the left and
right, respectively.
In an electrochemical redox system, two parameters controlling the overall rate of the
reaction are the charge transfer at the electrode/electrolyte interface and the mass transfer
from the bulk of the solution to the electrode surface. Based on these parameters, redox
systems are broadly classified into reversible, irreversible and quasi-reversible processes.
Comprehensive analysis of the cyclic voltammetric results reveal the reversibility of the
electrochemical processes and the details are discussed below [8, 11-12].
(i) Reversible System: This system obeys Nernst’s equation and rate of the electrochemical
process is controlled by diffusion (mass transfer) and not by charge transfer kinetics; hence,
diffusion is the rate controlling step. The key criterion for a reversible charge transfer process
is that Ep is independent of scan rate (υ) and the difference between Ep,c and Ep,a is close to
61
Ch. 3 - Experimental
the value of 2.3 RT/nF and is also independent of scan rate. The ratio of ip,a and ip,c is unity
and is independent of υ; the wave shape is also independent of scan rate. In a reversible
system, if both the reactant and product are soluble-soluble, then the relation between the
peak current and the scan rate is given by Randles-Sevick equation (Eq. 3.1).
ip
1
1
0.4463 nFC0 Aυ 2 D 0 2
Ep
Ep
2.2
2
nF
RT
1
2
(3.1)
RT
(3.2)
nF
where, n is the number of electrons involved in the charge transfer reaction, F is the Faraday
constant, A is area of the electrode (cm2), Co is the bulk concentration of electroactive species
(mol.cm-3), R is the gas constant, T is the absolute temperature (K), υ is the scan rate (V.s-1)
and Do is the diffusion coefficient (cm2.s-1) of the electroactive substance.
(ii) Irreversible System: In this system, a non-Nernstian path is totally followed and the rate
of the electrochemical process is controlled mostly by charge transfer kinetics. The main
criterion of the irreversible charge transfer kinetics is the shift in the peak potential with scan
rate. For instance, the cathodic peak potential shifts towards more negative potentials with
increase in scan rate. The relation between the peak current and diffusion coefficient for an
irreversible system is given by Delahay equation (Eq. 3.3).
i p,c
0.4958 nFAC0
ΔE p,c
αnFD 0
1
2
RT
1.15RT
α nαF
where ΔEpc is the shift in peak potential (Epc) for increase in scan rate by 10 times.
62
(3.3)
(3.4)
Ch. 3 - Experimental
In irreversible process, the peak separation (Epc - Epa) is very large and sometimes the reverse
peak (oxidation peak) cannot be seen in the scan reversal of the cyclic voltammogram and
also the wave shape is determined by α and is independent of scan rate. For the irreversible
process the following equations can be used to deduce the important parameters using cyclic
voltammetry
E
p
E
1.857RT
αn F
α
p
2
(3.5)
α - the charge transfer coefficient, is the measure of the symmetry of the energy barrier and
its value 0.1 ≥ α ≤ 0.9.
(iii) Quasi-reversible System: In quasi-reversible processes the rate of the electrochemical
reaction is a mixed control of both diffusion and charge transfer kinetics. In cyclic
voltammetry, the peak potential shifts with scan rate and the peak shape visually broadens as
scan rate is increased. If the difference between the cathodic and anodic peak potentials (ΔEp)
increases with scan rate and the average of the peak potentials ((Ep,a + Ep,c) / 2) is constant at
different scan rates, then the process could be quasi-reversible.
The heterogeneous charge transfer coefficient, ks, can be obtained by using Eq. (3.6),
which was proposed by Klingler and Kochi [8, 13].
kS
υF
2.18 D 0 (α n α )
RT
1
2
exp
α 2 nF
(E p,c
RT
E p,a )
(3.6)
The value of ks can also be obtained by Nicholson’s method using the following equation:
α
ks
ψ
D0
DR
2
1
πD 0
nF
υ
RT
63
(3.7)
2
Ch. 3 - Experimental
Depending upon the magnitude of ks, the electrode reaction can be classified [7] as reversible
when ks ≥ 0.3υ1/2 cm.s-1, quasi-reversible when 0.3υ1/2 ≥ ks ≥ 2 x 10-5υ1/2 cm.s-1 and
irreversible when ks ≤ 2 x 10-5υ1/2 cm.s-1.
3.4.2 Chronopotentiometry (Controlled Current Technique)
Chronopotentiometry (CP) is one of the well known voltammetric techniques, extensively
used to study the electrochemical behaviour. In this technique, the controlled current will be
applied between the working and counter electrodes using a galvanostat and the potential of
the working electrode versus reference electrode will be monitored/measured simultaneously.
The potential against time will be plotted as response and the plot is called as
chronopotentiogram. Different types of controlled current techniques are available based on
the type of current function applied [5, 14]. These include constant current
chronopotentiometry, chronopotentiometry with linearly increasing current, current reversal
chronopotetiometry and cyclic chronopotentiometry.
When the constant current is applied between the working and counter electrodes, the
concentration of the analyte ion decreases and the potential of the working electrode changes.
This process continues until the concentration of the analyte ion at the electrode becomes
zero. Since the concentration of the analyte ion changes with time, obviously, the potential of
the electrode also changes. The duration of this potential change or the concentration change
of the analyte ion is called as the transition time and is denoted by τ [15]. The transition time
can also be defined as the time, when the potential transition occurs after application of the
constant current [8]. The relation between the applied current and transition time was first
derived by H. J. S. Sand and is given in Eq. (3.8) [8, 11].
1
iτ
1
2
nFA(D0 π) 2 C 0
2
64
(3.8)
Ch. 3 - Experimental
The diffusion coefficient (D0) can be calculated from the experimentally determined value of
τ at a particular current, using Sand’s equation.
3.4.3 Electro-oxidation
Electro-oxidation is an electrochemical technique wherein the species of interest is oxidized
at the anode and it can be performed either by galvanostatic or potentiostatic mode. While
electroanalytical techniques deal with small surface area and transient time intervals, electrooxidation is carried out with larger electrode area for fairly longer time intervals and the
electrolyte solution is mechanically mixed to enhance the mass transport of the electroactive
species from the bulk of the solution to the electrode. The amount of species oxidized is
governed by Faraday’s First law: i.e. the amount of material evolved or deposited during
electrolysis is directly proportional to the quantity of the electricity passing through the
solution. The passage of 1 faraday (1F) or 96485 coulomb of electricity results in the
oxidation of 1 equivalent of material (1 mole of metal in an one-electron transfer) [8].
Therefore, it is possible to estimate the amount of oxidized material using Eq. (3.9).
Δm
i t
nF
C
nF
(3.9)
where Δm is the number of moles of material oxidized, i is the current in ampere, Δt is the
time in second, C is the charge passed in coulomb, n is the number of electrons transferred
and F is the Faraday’s constant. Equation (3.9) is obeyed only under the ideal condition,
where the faradaic or current efficiency, η is 100 %. In most of the cases, this value is less
than 100 %. Faradaic efficiency is defined by the relation,
η
Δm
100
Δm0
(3.10)
where Δm is the metal which is practically oxidized and Δm0 is the amount of oxidized metal
predicted by Faraday’s law for the passage of the Coulombic charge. Faraday’s laws govern
65
Ch. 3 - Experimental
the relationship between the coulombic charge and electrode-oxidized materials. Another
important aspect of electro-oxidation is the separation percentage of the material.
[Metal]
Separation %
Initial
[Metal]
[Metal]
Final 100
(3.11)
Initial
In a particular electro-oxidation process, if the overall separation and the rate of oxidation are
very low, the process becomes practically fruitless even if the value of η is ~100 %.
3.5 REFERENCES
1. Banks, C. V., O’Laughin, J. W., Anal. Chem., 29 (1957) 1412
2. Moore, G.L., Introduction to Inductively Coupled Plasma – Atomic Emission
spectroscopy, Elsevier Science, Amsterdam, The Netherlands, 3rd Edition, pp. 121, 1988
3. Boss, C.B., Fredeen, K.J., Concepts, instrumentation and techniques in inductively
coupled plasma optical emission spectrometry, Perkin Elmer, 2nd Edition, pp.36, 1997
4. Scholz, F., Electroanalytical methods: Guide to experiments and applications, 1st Edition,
Springer, Berlin, 2005
5. MacDonald, D.D., Transient techniques in electrochemistry, Plenum Press, New York,
1977
6. Galus, Z., Chalmers, R.A., Bryce, W.A.J., Fundamentals of electrochemical analysis, 2 nd
Edition, Ellis Horwood, New York, 1994
7. Kissinger, P.T., Heineman, W.R., Laboratory techniques in electro-analytical chemistry,
2nd Edition, Marcell Dekker, New York, 1996
8. Bard, A.J., Faulkner, L.R., Electrochemical methods - Fundamentals and applications, 2nd
Edition, Wiley, New York, 2001
9. Rossiter, B.W., Hamilton, J.F., Physical methods of chemistry: Electrochemicals
methods, Vol. II, Wiley, New York, 1986
66
Ch. 3 - Experimental
10. Kissinger, P.T., Heineman, W.R., J. Chem. Ed., 60 (1983) 702
11. Brown, E.R., Sandifer, J.R., Physical methods of chemistry- Volume II, Electrochemical
methods, Wiley, New York, 1986
12. Bamford, C.H., Compton, R.G., Electrode kinetics – principles and methods, Volume 26,
In Chemical Kinetics, Elsevier, Netherlands, 1986
13. Klingler, R.J., Kochi, J.K., J. Phys. Chem., 85 (1981) 1731
14. Delahay, P., New instrumental methods in electrochemistry: Theory, instrumentation and
application to analytical and physical chemistry, Interscience, New York, 1954
15. Paunovic, M., J. Electroanal. Chem., 14 (1967) 447
67